DESCRIPTION(Adapted from applicant's abstract): Phosphorylation of ion channels and receptors is a key mechanism that contributes to the regualtion of neuronal excitability. At the molecular level, it is thought that the targeted protein kinase activity is achieved by specific protein-protein interactions that contribute to the biochemical and subcellular specificity of the posttranslational modification. Recent studies have identified proteins that may mediate specific recruitment of phosphorylation machinery into a channel complex, providing exciting possibilities to understand spatially localized biochemical reactions in neurons. Potassium channels are key players in electrical excitability. The native molecular composition and functional organization of this large family of channels are largely unknown. This application seeks to investigate the molecular and functional organization of Shaker-like potassium channels. A central hypothesis is that posttranslational machinery is recruited by a specific anchor protein into a channel complex. The formation of a macromolecular complex confers the specificity and effectiveness of posttranslational modification on targeted channel proteins. The proposed experiments will utilize a combination of biochemical, molecular and electrophysiological approaches. The proposed study will be centered on a macromolecular complex including channel subunits, adapter proteins and associated protein kinases. The resultant information should provide important insights into the mechanisms of molecular diversity and functional plasticity of ion channel proteins. Potassium channels have been thought to play critical roles in a variety of biological processes. Defects in their subunit assembly and macromolecular organization have been implicated in human diseases, such as cardiac tachyarrhythmia. The molecular understanding of the events that are central to their regulated expression is therefore essential for developing our knowledge in the area of nerve function in health and in diseases.